The invention belongs to the technical field of nano catalysts, and discloses a method for synthesizing a monatomic catalyst, the monatomic catalyst and an application. The method comprises the following steps: (1) under an acidic condition, polystyrene nanospheres are taken as a sacrificial template, and a cyanamide compound, furfural and a metal source fully react to obtain a high polymer, wherein the cyanamide compound is one or more of cyanamide, dicyandiamide or melamine, and the metal source is one or more of a Fe source, a Co source, a Ni source, a Pt source, an Au source and a Pd source; and (2) high-temperature pyrolysis is performed on the high polymer in the atmosphere of protective gas to obtain the monatomic catalyst. The method disclosed by the invention is simple, can be used for synthesizing various metal monatomic catalysts, is a universal method, can be used for synthesizing the monatomic catalyst on a large scale, and overcomes the defects of complex synthesis and difficulty in large-scale preparation of other existing technologies. The catalyst disclosed by the invention is excellent in performance, is used for electrocatalytic chemical reaction and is used as an electrocatalyst.